Time-lapse stock footage of clouds in a brewing rainstorm (that never materialized, unfortunately), captured on April 1, 2006. Two versions of the footage are provided -- 2.5 minutes, and one sped up to 10 seconds.
Be aware that the video does have some noticeable horizontal lines. This just an artifact of the camera's CCD. The footage has been color-corrected to cut through the haze, and each frame is a blend of 10 frames, to limit the picture noise.